Thick water-in-silicone emulsions are useful in a number of personal care consumer products including antiperspirants, pigmented products such as liquid foundations, hair dressings, and skin moisturizers. Prior to the present invention, water-in-silicone emulsions were thickened by the addition of high-molecular weight silicones to the silicone phase of an emulsion.
Surprisingly, and contrary to conventional wisdom, it has now been discovered that dramatic thickening can be achieved by addition of a silicone latex to the water phase of a water-in-silicone emulsion, instead of adding a silicone latex to the silicone phase of the emulsion.
The addition of the silicone latex to the water phase provides several processing advantages. Since the latex is a water-based dispersion, it is most easily combined with the water phase prior to the preparation of the emulsion. Another advantage is that swelling of the latex particles is delayed until the silicone and water phases are brought together during emulsification. This keeps the viscosity of the two phases low and thereby facilitates processing.
The silicone latex is useful as a thickening additive when employed in a range of about 0.1 to 5.0 percent by weight of the emulsion. The amount of silicone latex depends upon the desired viscosity, and the phase volume ratio between the water phase and the silicone phase. The inherent viscosity of such an emulsion system without a thickener is determined primarily by the proportion of the water phase. The addition of a silicone latex to the water phase of the emulsion provides thickening over a range of different phase volume ratios.